S
saccharin
A compound, C7H5NO3S, that is several hundred times sweeter than can sugar and is used as a calorie-free sweetener.
salt
An ionic compound with a positive ion that comes from a base and a negative ion that comes from an acid.
silica
Silica is the common name for silicon dioxide, SiO2.It exists in nature as crystalline quartz.
smog
A fog containing fumes, or a photochemical haze caused by the action of ultraviolet radiation on hydrocarbons and NOx from automobile exhaust.
sol
A liquid colloidal dispersion; a fluid colloidal system in which solid particles are dispersed in a liquid colloidal solution.
solubility
The maximum amount of a substance that will dissolve in a given amount of solvent at a given temperature.
solute
The substance dissolved in a solution; substance present in a lesser amount in a solution.
solution
A homogeneous mixture of two or more substances.
solvent
The substance present in the largest amount in a solution; often the liquid component.
spectrometer
An instrument for measuring the emission or absorption of light of a particular wavelength.
spectroscopy
The science that deals with the use of the spectroscope and with spectrum analysis.A spectroscope is an optical device for producing and observing a spectrum of light or radiation from any source.
spin
The spin of an electron is designated by ms, the electron spin quantum number, which can have values of +1/2 and -1/2.In the presence of an external magnetic field an electron in an orbital can have one of two possible energy states, which depend on whether the magnetic field associated with the electron is aligned with or against the external magnetic field.
stereochemistry
The spatial arrangement of atoms in molecules or compounds and the relation of spatial arrangement to the substanceis properties.
stereoisomers
Two or more compounds with the same molecular formula and the same atom-to-atom arrangement, but with different arrangement of atoms in space. stereoisomeric (adjective)
steroids
Compounds containing a 17-carbon, four-ring system.
stoichiometry
The study of the quantitative relationships between reactants and products.
stratosphere
The layer of the earth's atmosphere that extends from roughly 7 miles (11 km) above the surface to 31 miles (50 km) above the surface.
sublimation
The direct conversion of a solid to a gas.
substituent
An atom or group that replaces another atom or group in a molecule.
superconductivity
A state in which the electrical resistance of a material is so low that it cannot be measured and appears to be zero.The superconducting state is also characterized by unusual magnetic properties.
supercritical
Above the critical point; above critical temperature or pressure.
supersaturated solution
A solution that temporarily contains more solute than the saturated amount at some temperature.
surface tension
The energy required to disrupt the surface of a liquid.